The invention herein lies in the art of braking systems and specifically in that of braking systems for aircraft. At the present, it is standard to utilize a plurality of brake disks, alternately keyed or splined to the axles and hubs of aircraft wheels, to achieve the imparting of a braking force to the wheels. The brake disks presently used have been quite satisfactory for their heat dissipating characteristics, but it has been found that the same have a tendency to wear and that continual adjustments are necessary to guarantee that brake pedal travel and brake force are substantially consistent with braking effort irrespective of the wear experienced by the brake disk stack. Such adjustment is also required to achieve maximum usage of the brake disks. It is most desirable that these adjustments be made on a continuing basis rather than periodically such that, for every braking effort, brake pedal travel and brake force bear the same relationship to each other.
Numerous approaches have been taken in the art to achieve the desired brake adjustment. It is presently known to use various standard types of adjusters wherein the adjustment technique is accomplished by a frictionally slidable unit maintained upon a tube. Using the standard brake adjuster mechanism, it has been found that a wide variance of loads exists for any given distance of brake pedal travel or brake application. That is, the force versus displacement curves of the present standard types of adjusters do not trace each other on successive brake applications as the brake disks wear. Indeed, the force necessary to overcome the frictional engagement between the tube and slidable unit varies with each brake application.
Another shortcoming utilizing the standard brake adjusters of the prior art is that static and dynamic coefficients of friction characterize the relationship between the tube and slidable unit. When brake pressure is initially applied, the first amount of travel experienced by the return mechanism is that known in the art as the built-in clearance. The next portion of travel is that compensating for the wear experienced during each braking effort. Above this, the force applied is that known as the effective brake force, i.e. the force actually being applied to stop the aircraft. However, with the static coefficient of friction being greater than the dynamic coefficient of friction, the force applied to effectuate movement of friction-based adjusters to compensate for brake wear must be sufficient to overcome both coefficients of friction and the return spring brake on force. Should the standard unit slip, the spring follower may then return to a point where there is no longer a built-in clearance. In such a case, the brake either remains in a locked position or, at best, suffers a loss of built-in clearance for subsequent brake applications.
Numerous approaches have been taken to resolve the problems inherent with the present standard brake adjusters. Teachings of such approaches are found in U.S. Pat. Nos. 2,888,109, and 3,542,165. Other teachings of some significance are found in U.S. Pat. Nos. 3,376,959; 3,958,670; and 3,990,547. Yet further, applicant's own U.S. Pat. No. 3,926,283, shows another novel approach toward a resolution of the problems presently existent in the art. The teachings of the foregoing prior art are of general interest with respect to the invention presented herein, but are not seen as particularly pertinent since such teachings themselves have inherent drawbacks. It will become apparent hereinafter that the instant invention provides significant advantages over these prior art teachings.